400 - Bad Request - This error occurs when we type the wrong URL and server as
no clue of what error is that.
401 - Unauthorized Request - When we try to access some page which are not authorized to view we get this error.
403 - Forbidden - If a page is blocked from our domain or we need a password to access that page we get this error.
404 - Not Found - This is the most common error that we get on net which means that the URL we are looking for as been removed or renamed.